itkPriorityQueueContainer.h

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/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkPriorityQueueContainer.h,v $
  Language:  C++
  Date:      $Date: 2008-10-12 12:46:48 $
  Version:   $Revision: 1.8 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notices for more information.

=========================================================================*/
#ifndef __itkPriorityQueueContainer_h
#define __itkPriorityQueueContainer_h

#include "itkObject.h"
#include "itkObjectFactory.h"
#include "itkVectorContainer.h"

#include <functional>
#include <queue>
#include <assert.h>
#include <vector>

namespace itk
{

// first define a common interface all the wrapper will have to abide to
// this will let us define our own wrapper with different behavior.
// As an exemple we define below a wrapper for a min sorted or max sorted
// queue.
template< typename TElement, typename TElementIdentifier = int >
class ElementWrapperInterface
{
public:
  typedef TElement                ElementType;
  typedef TElementIdentifier      ElementIdentifierType;

  ElementWrapperInterface() {}
  virtual ~ElementWrapperInterface() {}

  virtual TElementIdentifier GetLocation( const ElementType& element) = 0;
  virtual void SetLocation( ElementType& element, const ElementIdentifierType& identifier) = 0;
  virtual bool is_less( const ElementType& element1, const ElementType& element2 ) = 0;
  virtual bool is_greater( const ElementType& element1, const ElementType& element2 ) = 0;
};


//
// If you want to manage the items outside the queue for example, if you don't
// want the queue to manage the items memory, then you can use this wrapper
// around pointers to items.  It follows the ElementWrapperInterface and thus
// can be used in the queue.
//
template< typename TElementWrapperPointer, typename TElementIdentifier = int >
class ElementWrapperPointerInterface
{
public:
  typedef TElementWrapperPointer      ElementWrapperPointerType;
  typedef TElementIdentifier          ElementIdentifierType;

  ElementWrapperPointerInterface() { }
  ~ElementWrapperPointerInterface() { }

  TElementIdentifier GetLocation( const ElementWrapperPointerType& element)
    {
    return( (*element).GetLocation(*element) );
    }

  void SetLocation( ElementWrapperPointerType element, const ElementIdentifierType& identifier)
    {
    (*element).SetLocation(*element, identifier);
    }

  bool is_less( const ElementWrapperPointerType& element1, const ElementWrapperPointerType& element2 )
    {
    return( (*element1).is_less( (*element1), (*element2) ) );
    }

  bool is_greater( const ElementWrapperPointerType& element1, const ElementWrapperPointerType& element2 )
    {
    return( (*element1).is_greater( (*element1), (*element2) ) );
    }
};


// To follow ITK rule, we template the Element priority and the element
// identifier type.
// For example, as we want to use this for decimation, the element will be some
// kind of cell or point pointer, the priority will be whatever you want it to
// be as long as you define the comparison operators, and the identifier will
// set according to the size of the vector you want to create.
//
// this implementation is used for min sorted priorityqueue
template<
  typename TElement,
  typename TElementPriority = double,
  typename TElementIdentifier = int
 >
class MinPriorityQueueElementWrapper :
    public ElementWrapperInterface<
    MinPriorityQueueElementWrapper< TElement,
                                    TElementPriority,
                                    TElementIdentifier >,
    TElementIdentifier
    >
{
public:
  typedef TElement                ElementType;
  typedef TElementPriority        ElementPriorityType;
  typedef TElementIdentifier      ElementIdentifierType;

  ElementType                     m_Element;
  ElementPriorityType             m_Priority;
  ElementIdentifierType           m_Location;

  MinPriorityQueueElementWrapper() : m_Priority( 0 ), m_Location( -1 )
    {}

  MinPriorityQueueElementWrapper( ElementType element, ElementPriorityType priority ) :
    m_Element( element ), m_Priority( priority ), m_Location( -1 )
    {}

  virtual ~MinPriorityQueueElementWrapper() {}

  bool operator>( const MinPriorityQueueElementWrapper& other) const
    {
    return this->m_Priority > other.m_Priority;
    }

  bool operator<( const MinPriorityQueueElementWrapper& other) const
    {
    return this->m_Priority < other.m_Priority;
    }

  bool operator==( const MinPriorityQueueElementWrapper& other) const
    {
    return this->m_Priority == other.m_Priority;
    }

  ElementIdentifierType GetLocation( const MinPriorityQueueElementWrapper& element)
    {
    return element.m_Location;
    }

  void SetLocation( MinPriorityQueueElementWrapper& element, const TElementIdentifier& identifier)
    {
    element.m_Location = identifier;
    }

  // still virtual to be able to overload it in the Max flavor
  virtual bool is_less( const MinPriorityQueueElementWrapper& element1, const MinPriorityQueueElementWrapper& element2 )
    {
    return( element1 < element2 );
    }

  virtual bool is_greater( const MinPriorityQueueElementWrapper& element1, const MinPriorityQueueElementWrapper& element2 )
    {
    return( element1 > element2 );
    }

};

// this implementation is used for max sorted priorityqueue
// most of the job is already done, just need to overload the less
// and greater ops.
template<
  typename TElement,
  typename TElementPriority = double,
  typename TElementIdentifier = int
 >
class MaxPriorityQueueElementWrapper :
  public MinPriorityQueueElementWrapper< TElement,
                                         TElementPriority,
                                         TElementIdentifier >
{
public:
  typedef TElement                          ElementType;
  typedef TElementPriority                  ElementPriorityType;
  typedef TElementIdentifier                ElementIdentifierType;

  typedef MinPriorityQueueElementWrapper<ElementType,
                                         ElementPriorityType,
                                         ElementIdentifierType > Superclass;
  MaxPriorityQueueElementWrapper( ) :
    MinPriorityQueueElementWrapper< ElementType,
                                    ElementPriorityType,
                                    ElementIdentifierType >( ) {}

  MaxPriorityQueueElementWrapper( ElementType element,
    ElementPriorityType priority ) :
    MinPriorityQueueElementWrapper< ElementType,
                                    ElementPriorityType,
                                    ElementIdentifierType >( element, priority ) {}

  virtual ~MaxPriorityQueueElementWrapper() {}

  bool is_less( const MaxPriorityQueueElementWrapper& element1,
                const MaxPriorityQueueElementWrapper& element2 )
    {
    return( element1 > element2 );
    }
  bool is_less( const Superclass& element1,
                const Superclass& element2 )
    {
    return Superclass::is_less(element1, element2);
    }

  bool is_greater( const MaxPriorityQueueElementWrapper& element1,
                const MaxPriorityQueueElementWrapper& element2 )
    {
    return( element1 < element2 );
    }
  bool is_greater( const Superclass& element1,
                   const Superclass& element2 )
    {
    return Superclass::is_greater(element1, element2);
    }
};


// finally, implement the priority queue itself on top of an itk::VectorContainer
template<
  typename TElementWrapper,
  typename TElementWrapperInterface,
  typename TElementPriority = double,
  typename TElementIdentifier = int
  >
class PriorityQueueContainer :
  public VectorContainer< TElementIdentifier, TElementWrapper >
{

public:
  typedef PriorityQueueContainer                                    Self;
  typedef VectorContainer< TElementIdentifier, TElementWrapper >    Superclass;
  typedef SmartPointer<Self>                                        Pointer;
  typedef SmartPointer<const Self>                                  ConstPointer;

  typedef TElementIdentifier          ElementIdentifier;
  typedef TElementWrapper             Element;
  typedef TElementWrapperInterface    ElementInterface;

private:
  typedef Superclass                                    VectorType;
 // typedef typename VectorType::size_type              size_type;
//  typedef typename VectorType::VectorIterator         VectorIterator;
//  typedef typename VectorType::VectorConstIterator    VectorConstIterator;

public:
 PriorityQueueContainer():
   VectorType() {}
 //PriorityQueueContainer(size_type n):
 //   VectorType(n) {}
 //PriorityQueueContainer(size_type n, const Element& x):
 //  VectorType(n, x) {}
 PriorityQueueContainer(const Self& r): VectorType(r) {}

 template <class TInputIterator>
 PriorityQueueContainer(TInputIterator first, TInputIterator last):
   VectorType(first, last) {}

public:
  itkNewMacro(Self);
  itkTypeMacro(PriorityQueueContainer, VectorContainer);

  //void Reserve( ElementIdentifier NbOfElementsToStore )
  //{ this->Superclass->Reserve( NbOfElementsToStore ); }
  //void Squeeze( ) { this->Superclass->Squeeze( ); }
  void Clear( ) { this->Initialize( );  } // do not release memory
  bool Empty( ) const { return( this->empty() ); }
  void Push( Element element )
    {
    this->push_back( element );
    this->UpdateUpTree( static_cast< ElementIdentifier >( this->Size( ) ) - 1 );
    }

  Element Peek( )
    {
    assert( !Empty( ) );
    return( GetElementAtLocation( 0 ) );
    }

  void Pop( )
    {
    m_Interface.SetLocation( GetElementAtLocation( 0 ), -1 );
    if( this->Size( ) > 1 )
      {
      SetElementAtLocation( 0,
        GetElementAtLocation(
          static_cast< ElementIdentifier >( this->Size( ) - 1 ) ) );
      this->pop_back();
      UpdateDownTree( 0 );
      }
    else
      {
      if( this->Size() == 1 )
        this->pop_back();
      }
    }

  void Update( Element element )
    {
    ElementIdentifier location = m_Interface.GetLocation( element );
    assert( location != -1 );
    assert( location < static_cast< ElementIdentifier >( this->Size( ) ) );
    UpdateDownTree( location );
    UpdateUpTree( location );
    }

  void DeleteElement( Element element )
    {
    ElementIdentifier location = m_Interface.GetLocation( element );
    m_Interface.SetLocation( element, -1);

    assert( location != -1 );
    assert( location < static_cast< ElementIdentifier >( this->Size( ) ) );

    if( location == static_cast< ElementIdentifier >( this->Size( ) ) - 1 )
      {
      this->pop_back();
      }
    else
      {
      SetElementAtLocation( location,
        GetElementAtLocation( this->Size( ) - 1 ) );
      this->pop_back();
      UpdateDownTree( location );
      UpdateUpTree( location );
      }
    }

protected:

  // One instance of the interface to deal with the functions calls
  ElementInterface m_Interface;

  inline Element& GetElementAtLocation( const ElementIdentifier& identifier )
    {
    return this->operator[]( identifier );
    }

  inline void SetElementAtLocation( const ElementIdentifier& identifier,
    Element element )
    {
    this->operator[]( identifier ) = element;
    m_Interface.SetLocation( element, identifier );
    }

  inline ElementIdentifier GetParent( const ElementIdentifier& identifier ) const
    {
    return( (identifier - 1) >> 1 );
    }

  inline ElementIdentifier GetLeft( const ElementIdentifier& identifier ) const
    {
    return( (identifier << 1) + 1 );
    }

  inline ElementIdentifier GetRight( const ElementIdentifier& identifier ) const
    {
    return( (identifier << 1) + 2 );
    }

  void UpdateUpTree( const ElementIdentifier& identifier )
    {
    if( identifier > 0 )
      {
      ElementIdentifier id( identifier );
      Element element = GetElementAtLocation( id );
      ElementIdentifier parentIdentifier = GetParent( id );
      Element parent_element = GetElementAtLocation( parentIdentifier );

      while( ( id > 0 ) &&
          m_Interface.is_less( element, parent_element ) )
        {
        SetElementAtLocation( id, parent_element );
        id = parentIdentifier;
        if( id > 0 )
          {
          parentIdentifier = GetParent( id );
          parent_element = GetElementAtLocation( parentIdentifier );
          }
        }
      SetElementAtLocation( id, element );
      }
    }

  void UpdateDownTree( const ElementIdentifier& identifier )
    {
    ElementIdentifier id( identifier );
    Element element = GetElementAtLocation( id );

    ElementIdentifier queueSize =
      static_cast< ElementIdentifier >( this->Size( ) );

    while( id < queueSize )
      {
      ElementIdentifier childIdentifier = GetLeft( id );
      if( childIdentifier >= queueSize )
        {
        break;
        }
      if( ( childIdentifier + 1 < queueSize ) &&
          ( m_Interface.is_less( GetElementAtLocation( childIdentifier + 1 ),
                              GetElementAtLocation( childIdentifier ) ) ) )
        {
        ++childIdentifier;
        }
      Element temp = GetElementAtLocation( childIdentifier );
      if( m_Interface.is_less( element, temp ) )
        {
        break;
        }

      SetElementAtLocation( id, temp );
      id = childIdentifier;
      }

    SetElementAtLocation( id, element );
    }
};

}

#endif

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